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Ccts Level 2 > Cct > Flashcards

Cct Flashcards

1
Q

What do rectangular and polar vectors use?

A

Rectangular uses Y,X coordinates j =Y
Polar uses Hypotenuse, supplementary angle (magnitude, sin angle)

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2
Q

How to find average value 1 AC alternation.

A

Peak voltage X 0.637

100v x 0.637 = 63.7v

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3
Q

How to convert RMS (effective) to peak

A

Divide- rms /0.707 = peak

Rms100v / 0.707 = 141v

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4
Q

What is average DC voltage in AC sin wave

A

X 0.637 of peak of one alternation of AC sin wave. Full sin wave = 0 volts as positive and negative cancel each other out

100v peak alternation x 0.637 =63.7 volt

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5
Q

What is peak power and how do we work it out

A

Peak power in watts is peak volt X peak amp

100v x 15a = 1500watts

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6
Q

What is average power and how is it calculated?

A

Average power = peak power divided by 2 (halved)

Peak power 1500watts =750watts average

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7
Q

Frequency of generated emf is directly proportional to number of poles T/F

A

True- more poles= more emf

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8
Q

How many electrical degrees in 4 pole alternator

A

720 degrees
10 pole = 5 fields x 360= 1800

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9
Q

4 loop alternator creates 4 times emf than 1 loop t/f

A

True

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10
Q

What is prime mover

A

Machine / waterfall etc. that provided mechanical energy to alternator. Spins armature

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11
Q

What spins in simple alternator

A

Rotating armature with stationary field

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12
Q

What rotates in practical alternator

A

Rotating field and stationary armature

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13
Q

What part of alternator carry’s current to load?

A

Brushes

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14
Q

What is lenz law

A

Direction of induced emf must be such that any current resulting from it will develop a flux that will oppose direction

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15
Q
A
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16
Q

Faradays law equation?

A

E=blv

Current =flux X length X velocity

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17
Q

What is a cycle in sin wave

A

Cycle is one complete wave from 360 degree

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18
Q

What is period in sin wave

A

Time takes to complete one full cycle. Milliseconds

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19
Q

What is alternation in sin wave

A

One half of a full sin wave. Full sin wave contains 2 full alternations

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20
Q

What is amplitude of sin wave

A

Max height of wave form about 0 line/axis
Amplitude and maximum are the same

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21
Q

What is frequency in sine wave

A

Number of complete cycles in one seconds. Measured in Hz 60hz is standard in usa

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22
Q

What is instantaneous value on sine wave

A

The value at a particular instance of the time cycle frozen

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23
Q

How to work out instantaneous value?

A

Max voltage X Sin angle

100v x sin60 = 86.6v

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24
Q

Voltage max X Sin = what

A

Instantaneous value

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25
Fleming left hand rule. What does fingers point to?
Thumb = thrust (motion) Forefinger = Flux (field) Middle finger = current (amps)
26
Peak voltage and instantaneous on right triangle are which sides?
Peak = hypp Instantaneous = opp
27
Impedance triangle sides?
Impedance (Z)= hypotenuse reactance (X) = opposite Resistance (R) = adjacent
28
Power triangle sides?
Apparent power (AP) = hypotenuse Reactive power (RP) = opposite True power (TP)= adjacent
29
What’s is apparent power, reactive power and true power measured in?
Apparent = (VA) volt amps ( total power) Reactive = VAR ( volt amp reactive) True power = watts (W) power consumed
30
Quad 1,2,3,4 degrees?
Quad 1 = 0-90 Quad 2 = 90-180 Quad 3 = 180-270 Quad 4 = 270-360(0)
31
Pythagoras equ
C2 = A2 + B2
32
What are inductors
Made by winding wire into coil to maximise magnetic properties
33
3 types of inductors
Air core - high frequency high voltage Iron core- smooth chokes Variable inductor - can be adjusted by moving iron core
34
Where are variable inductors used
Radio receivers
36
If 1.5H coil has length of its core doubled what happens to its inductance
It’s halves 750H
37
What is CEMF
Counter - electro motive force Opposes applied voltage limiting current flow
38
What way does current flow through load and source
+ to - through source - to + through load
39
How to stop arcing at switch
Field discharge resistor Free wheel diode
40
Where is freewheeling diode placed
Parallel to inductor and reverse bias to source
41
Main purpose of inductor
Slow the rate of current rise in circuit and store energy in magnetic field
42
How many constants (TAU) does it take to reach full value current?
5 time constants
43
What is mutual induction?
changing magnetic field in one coil induces an electromotive force (EMF) or voltage in a nearby coil, even without any physical connection
44
What 4 things effect inductance
1: number of turns in coil 2: Permeability of core 3: Area of core 4: length of core
45
1 Tesla = what
1 Tesla = 1 webber/metre2 Conductor cut by 2 webber in 1 second = 2v ( 2 divide by 1 = 2
46
Does coil act as a load or source
Coil acts as a load converting electrical energy into magnetic ene er g
47
48
What is dielectric
Insulator in tween plates of capacitor Made of rubber / ceramic or air
49
What do inductors oppose change in?
Current
50
What do capacitors oppose change in
Voltage
51
What do Capacitors do?
Stores voltage up to source voltage. Then holds it and no more current can flow. Used to smooth power supply/energy storage
52
When does current flow in capacitor
Only when charging it discharging
53
Inductors store energy in what form Capacitors store energy in what form
Inductors : stores in magnetic field Capacitor : stores in electrostatic
54
Capacitor Plate with excess electrons is + or -?
Plate with excess electrons = + Lack of electrons = -
55
DCWV meaning
DC working voltage
56
Can a 120v dc capacitor be used in 120v ac?
No as AC current uses peak voltage not RMS 120v x.707= 169v would damage 120v capacitor would need a capacitor rated for 170v
57
Closer plates and longer plates in capacitor = more or less force/energy storage?
More energy stored
58
After 5 time constants what happens to capacitor
Resistor drops voltage and capacitor now source voltage. Switches around
59
60
Advantages of AC?
Can be stepped up over long distances (power lines) Smaller/ cheaper / more durable
61
Advantages of DC
Needed to make electromagnet Electrochemical Modern electronics Cathodie protection
62
What are SHRED effects.
S (skin effect) higher frequency issue H (hysteresis loop) magnetism R ( radiation loss) E (eddy currents. Use laminations to stop) D (dielectric loss) stretching
63
How to test AC effective resistance?
With watt metre and Ammetre R= P / I2
64
65
66
67
68
Property of a cct that opposed change in voltage
CAPACITANCE
69
Property of cct that opposes change in current
INDUCTANCE
70
What is impedance, resistance and reactance measured in?
Impedance (Z) Resistance (R) Reactance (X) ALL MEASURED IN OHMS
71
What is Tesla measurement of
Magnetic flux
72
What does trimmer capacitor change
Distance between plates
73
What does variable capacitor change
Area of plate
74
Three dimensional region electric charge =
Electrostatic field
75
Maximum field intensity an insulator can withstand is called?
Dialectic strength
76
77
How to get average power from peak power
Average power is always half of peak power. NEVER USE 0.637 in POWER
78
Light is bright when swtich is initially closed in cct with capacitor. True or false
True - capacitor gives a surge of power so light will be bright until 5 tau then light will go off
79
What is 3 dimensional region an electric charge is acted upon by electric force?
Electrostatic field
81
Where are inductors used
Lighting ballasts Transformers Chokes Coils

Ccts Level 2 (1 decks)

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